$53.50
step-by-step explanation:
you have to subtract the amount of money chuck earned ($72.50) by the cost of the gas for the mower ($11.25) and the new string for the trimmer he bought ($7.75).
72.50-11.25=61.25
and then subtract $61.25 by the second thing he bought (the new string for the trimmer)
61.25-7.75=53.5
so in total it's $53.50 (53 dollars and 50 cents)